This invention relates to borescopes and endoscopes, which are long flexible instruments which carry a viewing device at the end of an elongated insertion tube. Borescopes are intended for inspection of concealed machine parts and the like, for example, inspection of vanes of a turbine or jet engine without disassembly of same. Endoscopes are intended for examination of a human body cavity.
The invention is more particularly related to a viewing head which is demountably installed on the distal end of a borescope insertion tube.
For small borescopes, such as those of six mm diameter, a right angle optical assembly is often required. This should be detachable so that the borescope can be used for both forward viewing and side viewing, but the viewing assembly must not fall off while in use. The current approach to attachments for borescope or endoscope viewing heads is the use of threaded retaining rings and keyed structure for orientation of the optics. Bayonet attachment devices are sometimes used also. However, conventional devices are often difficult to install or remove, or else do not hold the attachment onto the borescope securely enough to ensure that the assembly will not fall off. These devices have also been impractical where a large (i.e., 5 mm) video imager is employed in a small diameter (i.e., 6 mm) borescope.